JP2024021808A - Catalytic body and method for manufacturing the same - Google Patents

Abstract

To improve a point that the maximum catalytic reaction could not conventionally be obtained by the minimum use of a catalyst substance.SOLUTION: A catalytic body of the present invention is a catalytic body in which a catalyst layer made of a catalyst substance and a carrying substance is formed, where the catalyst substance is segregated on a surface of the catalyst layer.EFFECT: In the catalyst layer, because the catalyst substance is segregated on a surface contacting a reactant, useless catalyst substance is not present inside the catalyst layer, the necessary lowest catalyst substance can be used effectively and to the maximum.SELECTED DRAWING: Figure 2

Description

The present invention relates to a catalyst body in which the amount of catalyst material used and reaction efficiency are optimized, and a method for manufacturing the same.

For example, in Patent Document 1 (Japanese Unexamined Patent Publication No. 2012-240002), a catalyst body in which a catalyst layer consisting of a catalyst substance and a supporting substance is formed on a base material is a catalyst layer formed on the surface of platinum particles made of platinum or a platinum alloy, or In order to easily mass-produce a catalyst in which the surface of the platinum particles of a conductive carrier supporting platinum particles is coated with a copper layer without using an external power source, an acid aqueous solution containing copper ions is applied to the platinum particles or A precipitation step in which a copper material is immersed in a suspension suspended in a conductive carrier to deposit a copper layer on the surface of the platinum particles, and in conjunction with the precipitation step, a copper layer is deposited on the surface of the platinum particles in the precipitation step. An evaluation step for evaluating the condition, an immersion step for immersing the reference electrode and a working electrode made of platinum or a platinum alloy in a suspension, and stirring the suspension to deposit a copper layer on the surface of the working electrode. However, a series of steps consisting of a measuring step of measuring the time until the potential of the working electrode with respect to the reference electrode becomes a constant potential, and a removing step of removing the copper layer deposited on the working electrode after the measuring step, It is disclosed that the precipitation process is completed and obtained based on the amount of change at each measurement time in the measurement process by repeating the measurement process.

For example, in Patent Document 2 (Japanese Unexamined Patent Publication No. 5-220394), ceric sulfate and alumina powder are combined to have a large oxygen storage capacity and to be able to support cerium oxide with good dispersibility on a carrier. When an alkali is added to the suspension and cerium hydroxide is precipitated on the surface of the alumina powder by hydrolysis, the reaction to precipitate cerium hydroxide on the alumina powder surface is completed when the pH of the reaction solution is 12.0 or less, and the surface It is disclosed that alumina powder having precipitated cerium hydroxide is washed, dried and calcined.

As mentioned above, conventionally, in order to obtain a catalytic body, it is a known technique to use a suspension of a catalytic material and a supporting material, or to precipitate a catalytic material on a supporting material.

However, the conventional method has the following problems. Conventional methods have the problem of not taking into account that catalytic efficiency is influenced by where the precipitates appear and what kind of properties (states) they appear in.

For example, in a catalytic reaction in the gas phase, if a precipitate, that is, a catalytic substance appears in the lower layer of the catalyst layer, contact with the catalyzed substance to be catalyzed will be insufficient, and the catalytic substance will not be absorbed into the interior of the supported material. If the catalyst material appears dispersed, the catalyst material deposited at internal locations other than the contact surface does not contribute to the catalytic reaction and is wasted.

In particular, the catalytic materials used in many of the catalytic reactions that are attracting attention these days are rare non-metals that belong to the so-called noble metals and rare metals, so it is difficult to obtain the maximum catalytic reaction with the minimum use of catalytic materials. Although this is considered to be a serious concern, in the past, the only way to facilitate mass production was to uniformly disperse the catalyst material in the catalyst layer.

Japanese Patent Application Publication No. 2012-240002 Japanese Patent Application Publication No. 5-220394

The problem sought to be solved is that conventional catalysts and manufacturing methods do not provide maximum catalytic reactivity with the minimum amount of catalytic material used.

In order to solve the above problems, the catalyst body of the present invention has a structure in which the catalyst substance is segregated on the surface of the catalyst layer in the catalyst body in which a catalyst layer consisting of a catalyst substance and a supporting substance is formed.

Further, in order to solve the above problems, the method for manufacturing a catalyst body of the present invention is a method for manufacturing a catalyst body in which a catalyst layer consisting of a catalyst material and a supporting material is formed on the surface of a base material, the method comprising: A suspension of the supported material was prepared, and a catalyst layer in which the catalyst material was segregated on the surface was formed using this suspension on the surface of the substrate.

According to the present invention, in the catalyst layer, the catalyst substance is segregated on the surface that contacts the catalyzed substance, so there is no wasteful catalyst substance that does not contribute to the catalytic reaction inside the catalyst layer, and therefore the necessary minimum catalytic material can be used effectively and maximally.

(a) is a conceptual diagram for explaining a precipitation state, and (b) is a conceptual diagram for explaining a surface segregation state, respectively. FIG. 3 is a conceptual diagram for explaining the surface segregation state in the catalyst layer of the catalyst body of the present invention. FIG. 3 is a diagram showing an example of a combination of a catalyst material and a supporting material. FIG. 3 is a diagram showing an example of a combination of a catalyst material and a supporting material. FIG. 3 is a diagram showing an example of a combination of a catalyst material and a supporting material.

The present invention aims to use the minimum necessary amount of catalytic material effectively and with maximum performance in a catalytic body in which a catalytic layer consisting of a catalytic material and a supporting material is formed on the surface of a base material. This was achieved by making it segregated on the surface of the catalyst layer.

The present invention also provides a method for producing a catalyst body in which a catalyst layer consisting of a catalyst substance and a supported substance is formed on the surface of a base material in order to obtain the above-mentioned catalyst body, wherein the catalyst substance and the supported substance are suspended. A suspension was prepared, and a catalyst layer in which the catalyst substance was segregated on the surface was formed using this suspension on the surface of the substrate.

The principle and mechanism of the present invention will be explained.
Surface segregation, as an academic term, means a state in which precipitation is concentrated on the surface. In the present invention, in the catalyst layer consisting of a catalyst material and a supporting material (and an inorganic material: claims 2 and 4), the catalyst material in the supporting material is on the surface opposite to the base material (hereinafter referred to as "surface"). ) means that the precipitation is concentrated. Images of the precipitation state and surface segregation are shown in FIGS. 1(a) and 1(b), respectively.

First, in a catalyst body that has surface segregation, the efficiency of the catalytic reaction tends to improve as more catalytic material appears on the surface per unit area than in the state where it is precipitated inside. In extreme cases, when catalyst substances segregate over the entire surface, as shown in Figure 1(b), the catalyst substances on the surface become stable at the atomic level, reducing the number of active atoms and increasing the number of exposed atoms. The efficiency of the catalytic reaction with the catalytic material decreases. Further, in the state shown in FIG. 1(b), the catalyst material that does not come into contact with the catalytic material remaining inside the catalyst layer (the layer below the surface layer) is wasted.

As shown in FIG. 2, in the present invention, even if some catalyst material remains inside the catalyst layer, an amount of the catalyst material that can be dispersed on the surface is used, and most of the catalyst material is transferred to the catalyzed material. It was constructed so that it could contribute to the catalytic reaction with. As a result, a necessary and sufficient catalytic reaction can be obtained with a reduced amount of catalyst material used (compared to conventional methods), that is, a catalytic reaction with maximum efficiency can be obtained for the amount of catalyst material used.

That is, the present invention is a catalyst body in which a catalyst layer consisting of a catalyst material and a supporting material is formed, in which the catalyst material is segregated on the surface of the catalyst layer.

The present invention referred to Michiko Yoshibu, "Simulation of surface segregation prediction - SurfSeg: under vacuum and oxygen atmosphere" (Surface Science Vol. 34, No. 7, pp. 340-345, 2013) (hereinafter referred to as "References ). That is, the present invention referred to reference documents and SurfSeg and found conditions under which it is possible to reliably and easily grasp the combination of substances that cause surface segregation.

In the reference literature, the diffusion phenomenon that occurs between substrate element A and film metal B when a metal film with a laminated structure is heated to a temperature that causes grain boundary diffusion, and further heats to such a degree that body diffusion occurs, is as follows. Whether (a) the substrate element A segregates on the surface of the film metal B, or (b) interdiffuses at the interface between the substrate element A and the film metal B, is determined by annealing in vacuum or in an oxygen atmosphere. At the same time, it is stated that simulations (predictions) were performed using SurfSeg, and the accuracy of the predictions was verified.

Regarding the principle of (a) surface segregation and (b) interdiffusion during vacuum annealing under the above conditions, quoting the reference literature, ``The atoms of the substrate are thermally excited and are always adsorbed to the film grain boundaries with a certain probability. . At this time, if the state of atoms adsorbed to the film grain boundaries is more stable, these atoms do not return to the substrate, but are transported to the film surface (following the concentration gradient) and segregated on the film surface. On the other hand, if it is more stable to return to the substrate than to be adsorbed to the film grain boundaries, the atoms will return to the substrate side, the substrate elements will not be transported to the film surface, and no segregation will be observed.'' There is.

That is, during vacuum annealing, the presence or absence of surface segregation is determined depending on whether the substrate element A is adsorbed to the film material or the substrate material for energetic stability. From this, the former in the above quotation corresponds to (a), the energy of substrate element A adsorbed onto film metal B (A on B), and the latter in the above quotation correspond to (b), The energy of adsorption (A on A) of the substrate element A onto the substrate metal A, and the energy of (A) is smaller than that of (B), that is, (A) is smaller than (B). Surface segregation occurs during instability.

In the present invention, the catalyst material is segregated on the surface of the catalyst layer, and in order to achieve this state, a suspension of the catalyst material and the supporting material is created, and this suspension is applied to the surface of the base material. , forming a catalyst layer in which the catalyst substance is segregated on the surface (described later).

Segregation of the catalyst material on the surface of the catalyst layer means that the catalyst material is segregated on the surface of the entire catalyst layer (consisting of the catalyst material and the supporting material) opposite to the side supported on the substrate, that is, the relationship on the substrate. This means that the catalyst substance is segregated on the surface of the supported material. Therefore, a combination that provides the above energy difference (A on B) < (A on A) is essential between the catalyst material and the supporting material.

Here, the substrate element (substrate material) A in the above-mentioned reference document is replaced with the "catalyst material" of the present invention, and the membrane metal (film material) B is replaced with the "support material" of the present invention, and the following figures are shown below. 3 to 5 will be explained. Figures 3 to 5 show the heat of formation when metals are mixed, values (kJ/mol) obtained by the so-called Miedema equation (omitted); the upper side is (A on B) = Ea, and the lower side is (A on B) = Ea. on A)=Eb.

The SurfSeg simulator in the reference can only simply determine (A on B) < (A on A), but in the present invention, from this, a combination such as Eb-Ea≧6kJ/mol, preferably Eb It has been found that if the combination is such that -Ea≧10 kJ/mol, the catalyst substance can be reliably segregated on the surface of the supporting material.

As shown in FIGS. 3 to 5, using minerals that can be generally used as catalyst materials as examples, the following combinations cause surface segregation. In FIGS. 3 to 5, the areas colored in gray are combinations where the Eb-Ea is less than 6 kJ/mol, that is, examples of combinations in which the catalyst substance does not segregate on the surface.

When the catalyst material is "silicon (Si)", the supported material can be Ag, Al, La, Au, Mn, Cu, Pd, Fe, Ni, Cr, Co, Pt, Zr, Ti, Rh, V, Mo. , Ru, Ir, Ta, W, etc., silicon can be segregated on the surface.

When the catalyst material is "silver (Ag)", the supporting material is Al, Sr, La, Au, Mn, Cu, Pd, Fe, Ni, Cr, Co, Pt, Zr, Ti, Rh, V, Mo. , Ru, Ir, Ta, W, etc., silver can be segregated on the surface.

When the catalyst material is "aluminum (Al)", the supported material is Si, Ag, La, Au, Mn, Cu, Pd, Fe, Ni, Cr, Co, Pt, Zr, Ti, Rh, V, Mo. , Ru, Ir, Ta, W, etc., aluminum can be segregated on the surface.

When the catalyst material is "strontium (Sr)", the supporting material is Si, Ag, Al, La, Au, Mn, Cu, Pd, Fe, Ni, Cr, Co, Pt, Zr, Ti, Rh, V , Mo, Ru, Ir, Ta, W, etc., strontium can be segregated on the surface.

When the catalyst material is "lanthanum (La)", the supported material is Si, Ag, Al, Au, Mn, Cu, Pd, Fe, Ni, Cr, Co, Pt, Zr, Ti, Rh, V, Mo. , Ru, Ir, Ta, W, etc., lanthanum can be segregated on the surface.

When the catalyst material is "gold (Au)", the supported material is Al, Sr, La, Mn, Cu, Pd, Fe, Ni, Cr, Co, Pt, Zr, Ti, Rh, V, Mo, Ru. , Ir, Ta, W, etc., it is possible to segregate gold on the surface.

When the catalyst material is "manganese (Mn)", the supported material is Au, Cu, Pd, Fe, Ni, Cr, Co, Pt, Zr, Ti, Rh, V, Mo, Ru, Ir, Ta, W. , etc., it is possible to segregate manganese on the surface.

When the catalyst material is "copper (Cu)", the supporting material is Pd, Fe, Ni, Cr, Co, Pt, Zr, Ti, Rh, V, Mo, Ru, Ir, Ta, W, etc. This allows copper to be segregated on the surface.

When the catalyst material is "palladium (Pd)", the supported material is Sr, La, Mn, Cu, Fe, Ni, Cr, Co, Pt, Zr, Ti, Rh, V, Mo, Ru, Ir, Ta. , W, etc., palladium can be segregated on the surface.

When the catalyst material is "iron (Fe)", iron can be segregated on the surface by using Pt, Zr, Ti, Rh, V, Mo, Ru, Ir, Ta, W, etc. as the supporting material. .

When the catalyst material is nickel (Ni), nickel can be removed by using Fe, Cr, Co, Pt, Zr, Ti, Rh, V, Mo, Ru, Ir, Ta, W, etc. as the supporting material. It can be surface segregated.

When the catalyst material is "chromium (Cr)", chromium can be removed by using Fe, Ni, Co, Pt, Zr, Ti, Rh, V, Mo, Ru, Ir, Ta, W, etc. as the supporting material. It can be surface segregated.

When the catalyst material is "cobalt (Co)", the cobalt can be segregated on the surface by using Fe, Cr, Pt, Zr, Ti, Rh, V, Mo, Ru, Ir, Ta, W, etc. as the supporting material. can be done.

When the catalyst material is "platinum (Pt)", the supporting material is La, Mn, Fe, Ni, Cr, Co, Zr, Ti, Rh, V, Mo, Ru, Ir, Ta, W, etc. This allows platinum to be segregated on the surface.

When the catalyst material is "zirconium (Zr)", the supporting material can be Au, Cu, Pd, Fe, Ni, Cr, Co, Pt, Ti, Rh, V, Mo, Ru, Ir, Ta, W, etc. By doing so, zirconium can be segregated on the surface.

When the catalyst material is "titanium (Ti)", the supporting material is Au, Cu, Pd, Fe, Ni, Cr, Co, Pt, Rh, V, Mo, Ru, Ir, Ta, W, etc. This allows titanium to be segregated on the surface.

When the catalyst material is "rhodium (Rh)", rhodium can be segregated on the surface by using Fe, Cr, Zr, Ti, V, Mo, Ru, Ir, Ta, W, etc. as the supporting material. .

When the catalyst material is "vanadium (V)", the vanadium can be segregated on the surface by using Pd, Fe, Ni, Co, Pt, Rh, Mo, Ru, Ir, Ta, W, etc. as the supporting material. Can be done.

When the catalyst material is "molybdenum (Mo)", molybdenum can be segregated on the surface by using Pt, Rh, Ru, Ir, Ta, W, etc. as the supporting material.

When "ruthenium (Ru)" is used as the catalyst material, ruthenium can be segregated on the surface by using Zr, Ti, V, Mo, Ir, Ta, W, etc. as the supporting material.

When "iridium (Ir)" is used as the catalyst material, iridium can be segregated on the surface by using Zr, Ti, V, Mo, Ta, W, etc. as the supporting material.

When the catalyst material is "tantalum (Ta)", tantalum can be segregated on the surface by using Pt, Rh, Ru, Ir, W, etc. as the supporting material.

When "tungsten (W)" is used as the catalyst material, tungsten can be segregated on the surface by using Ir, Ta, etc. as the supporting material.

As described above, the present invention calculates the energy per amount of material (Eb ) and the energy (Ea) per amount of substance when adsorbed on the catalyst substance itself, which is a combination such that Eb - Ea ≧6 kJ/mol, allows the catalyst substance to freely segregate on the surface. It is possible to suppress residual catalytic material that does not contribute to the catalytic reaction inside the layer, and it is possible to reduce the amount of catalytic material used.

Furthermore, in the present invention, the catalyst layer may include not only a catalyst material and a supporting material, but also an inorganic material added thereto. By adding an inorganic substance, the catalytic material segregated on the surface can be appropriately dispersed, and gas adsorption properties are improved in the gas phase reaction, making the catalytic reaction even better.

Note that even when adding an inorganic compound substance, that is, when the catalyst layer is formed using a supporting substance other than the catalyst substance or an inorganic compound substance, in addition to the above combination of Eb-Ea≧6 kJ/mol, the inorganic compound C (C on C) - (C By considering B)≧6kj/mol, not only the catalyst substance but also the inorganic compound can be segregated on the surface.

Further, in forming the catalyst layer on the surface of the base material, the present invention prepares a suspension of the catalyst material and the supporting material, and performs this suspension on the base material by means such as vapor deposition, thermal spraying, etc. That's fine. Note that this suspension may contain an inorganic compound.

The suspension of each substance that forms the catalyst layer may be one in which the nuclear substance is dispersed in a predetermined amount of water; if it precipitates quickly, add viscosity to the water. You can. By doing so, a catalyst layer in which the catalyst substance is uniformly dispersed is formed on the base material, and surface segregation occurs reliably on the base material.

Furthermore, in the present invention, when creating a suspension, the particle size of each substance may be less than 1 μm, or the molecules or molecular aggregates containing each substance may be less than 1 μm. By making the particles finer in this way, the surface segregation of the catalyst material occurs reliably and quickly, and the dispersion of the catalyst material on the surface is also ensured.Therefore, the amount of catalyst material used can be suppressed and the maximum reaction efficiency can be obtained.

Claims (5)

A catalyst body in which a catalyst layer made of a catalyst substance and a supporting substance is formed on the surface of a base material, wherein the catalyst substance is segregated on the surface of the catalyst layer. 2. The catalyst body according to claim 1, wherein a surface-segregated catalyst substance is dispersed in the catalyst layer by an inorganic substance. A method for manufacturing a catalyst body in which a catalyst layer consisting of a catalyst material and a supporting material is formed on the surface of a base material, the method involves creating a suspension of the catalyst material and supporting material, and using this suspension to form a catalyst layer on the surface of the base material. A method for producing a catalyst body, which forms a catalyst layer on the surface of which a catalyst substance is segregated. 4. The method for producing a catalyst body according to claim 3, wherein the suspension contains an inorganic compound. 5. The method for producing a catalyst body according to claim 3, wherein the particle size of each substance or the molecule or molecular aggregate containing each substance is reduced to less than 1 μm before creating the suspension.

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